[css-rythm-1] [editorial] remove redundant px dimension from line-height-step initial value

[keithamus]

The line-height-step property in css-rythm-1 defines its initial value as 0px. AIUI - it being a zero value means the px is redundant.

It seems to be more common to use 0 rather than 0px. In fact here are all the places that have an initial of 0:

• css-box (margin*, padding*)
• css-scroll-snap (scroll-margin*)
• css-inline (baseline-shift)
• css-shapes (shape-margin, shape-padding)
• css-text (text-indent, line-padding, hyphenate-limit-zone)
• css-text-decor (text-decoration-trim)
• css-ui (outline-offset)
• css-borders (border-*-radius & border-radius)
• css-logical (okay maybe an unfair comparison as it's mostly logical equivalents of box/borders)

And here are the places that have an initial of 0px:

• css-rythm (line-height-step - that's this one)
• css-tables (border-spacing - this initial value is 0px 0px)
• css-animation (animation-delay - 0s)
• css-animation (transition-delay, transition-duration - both 0s)
• css-overflow (overflow-clip-margin* - all 0px)
• css-backgrounds (background-position* - all 0%)

If this PR gets merged I'll follow up with one correcting css-overflow and perhaps the others 😉

[cdoublev]

If I am not mistaken, only zero <length> outside math functions can be unitless (and zero <angle> in some places explicitly allowing it), which seems to be a legacy thing (akin to <quirky-length>) so leaning towards 0px seems more appropriate imo, as this evidently leads people to make wrong assumptions.